title: An easy-to-implement filter for separating photo-excited signals from topography in scanning tunneling microscopy.
abstract: In order to achieve elemental and chemical sensitivity in scanning tunneling microscopy (STM), synchrotron x-rays have been applied to excite core-level electrons during tunneling. The x-ray photo-excitations result in tip currents that are superimposed onto conventional tunneling currents. While carrying important physical information, the varying x-ray induced currents can destabilize the feedback loop causing it to be unable to maintain a constant tunneling current, sometimes even causing the tip to retract fully or crash. In this paper, we report on an easy-to-implement filter circuit that can separate the x-ray induced currents from conventional tunneling currents, thereby allowing simultaneous measurements of topography and chemical contrasts. The filter and the schematic presented here can also be applied to other variants of light-assisted STM such as laser STM.
authors.affiliation: Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA.
authors.forename: Kangkang
authors.initials: K
authors.lastname: Wang
authors.forename: Daniel
authors.initials: D
authors.lastname: Rosenmann
authors.forename: Martin
authors.initials: M
authors.lastname: Holt
authors.forename: Robert
authors.initials: R
authors.lastname: Winarski
authors.forename: Saw-Wai
authors.initials: SW
authors.lastname: Hla
authors.forename: Volker
authors.initials: V
authors.lastname: Rose